//只有 int， double， String， bool, null, List, 或者 Map 类型对象可以直接编码成 JSON

import 'package:flutter_test/flutter_test.dart';

main() {
  test("test", () {
    var a;
    a ??= 3;
    a ??= 4;
    print("a is $a");

    _Test b;
    var c = b?.result() ?? 6;
    print("c is $c");
  });
}

class _Test {
  int result() {
    return 5;
  }
}
